Applicant incorporates by reference U.S. Pat. No. 6,367,462, entitled Engine Torque Management Method with High Dilution EGR Control, issued to McKay, et al., in that the method for engine torque management need not be fully described in detail herein.
This invention pertains generally to oil control valves for use in internal combustion engines, and more specifically to a method and apparatus to clean an oil control valve.
Engine manufacturers have incorporated oil control valves to operate and control actuators that are part of systems for variable cam phasing, cylinder deactivation, and variable valve lift and duration, among others. A system will use the oil control valve to divert flow of pressurized engine oil and drive the actuator to accomplish a desired work output. By way of example, an oil control valve used in conjunction with a variable cam phaser can be used to accomplish variable opening time of an intake or exhaust valve, relative to a position of a piston. The system uses the oil control valve to control the flow of engine oil to the variable cam phaser that is attached to a camshaft of the engine, based upon a command from an engine controller. Distinct engine performance benefits that are realized from the use of variable cam phasing include an improvement in combustion stability at idle, improved airflow into the engine over a range of engine operations corresponding to improvements in engine performance, and improved dilution tolerance. This will result in such benefits as improved fuel economy, improved torque at low engine speeds, lower engine cost and improved quality through elimination of external exhaust gas recirculation (EGR) systems, and improved control of engine exhaust emissions.
The oil control valve has a fluid control portion that is driven by an electromagnetic solenoid. The fluid control portion of the oil control valve is comprised of a valve body and an internal spool. There are two separate openings in the valve body that are in fluid connection with two separate sides of the variable cam phaser. The internal spool has an oil inlet and two separate outlets that correspond to and overlap with the two openings in the valve body. Pressurized engine oil flows through the valve to the two sides of the variable cam phaser.
The oil control valve operates by controlling the amount of the overlap between the openings in the valve body and the spool. This controls the relative flow of oil out of each of the two separate openings to the variable cam phaser. The control of the relative flow controls the relative pressures on each side of the variable cam phaser, which determines the position of the phaser and hence the event timing of the engine valves.
There is a possibility that the performance of the variable cam phasing system will be reduced due to the inability of the oil control valve to control flow and pressure to the two sides of the phaser. This loss of control can be a result of some form of contamination of the valve by engine oil. A typical engine oil filtering system will remove particle sizes above 25 microns in diameter. Particles contained in the oil that are smaller than 25 microns will pass freely with the oil. In most areas of engine operation, this has not proven to be a problem in-use. However, in an oil control valve, contaminants can become pinched between the spool and the valve body, wherein the contaminants become caught in a scissors-like action between a land opening in the spool and a metering edge on the valve body. Also, manufacturing clearances between a valve body and inner spool of the oil control valve are typically much less than 100 microns. Contaminants in the oil may become wedged between the spool and valve body. Either of the actions of pinching or wedging can result in a reduction in response time of the valve or a reduction in the range of motion of the valve, with a corresponding reduction in the valve""s ability to control flow to the variable cam phaser. When this happens, the benefits derived from a variable cam phasing system may be compromised by the reduction in valve performance.
The prior art with respect to cam phasing has addressed flow and reduced performance issues by making the grooves in the oil control valve larger than needed to ensure adequate flow to through the valve. This action can reduce dynamic flow control range of the valve. In analogous situations, such as when the valve control system was used in an automatic transmission, the prior art has employed dithering methods, i.e. induced oscillations of a valve at a preset frequency and amplitude, to vibrate the valve to remove grit. Dithering of sufficient amplitude to clean a valve under some operating conditions of an automatic transmission can lead to unacceptable vibration in a clutch or gear shift-shock. Manufacturers of hydraulic propulsion systems have used flush systems to clean and cool hydraulic fluid. The flush system will have high pressure on one side of the valve and a drain to a reservoir on the other side of the valve. The flush system allows flow of a quantity of fluid over the valve to perform a cleaning action.
Hence, there is a need for a method to perform cleaning actions on an oil control valve used in an internal combustion engine to maintain sufficient oil flow and pressure over the life of the engine. There is also a need to perform the cleaning action in a manner that will not disrupt engine operation. Maintaining sufficient flow through the oil control valve will help ensure the ability of an engine system that uses an oil control valve to function as intended to maintain flow control over the range of operation, in order to derive the benefits of the system. Any cleaning method must be transparent to the vehicle operator, in that there should be no deterioration in engine operating performance when the method is actuated. There is also a need to operate the cleaning method in response to the detection of a fault, and in response to an external service command.
The present invention is an improvement over conventional engine systems that employ oil control valves in that it provides a method to clean the oil control valve by actuating the valve when specific entrance criteria are met. This will ensure on-going cleaning of the valve to remove contaminants that are wedged, pinched or otherwise trapped on the valve without interference in the operation of the vehicle.
The invention removes contaminants from an oil control valve in an internal combustion engine. It includes providing the engine with the oil control valve, at least one sensor, a controller, a fuel injection system, a fault detection system, and an external communicator. The invention determines when the engine is operating in a predetermined mode, and executes an oil control valve cleaning routine at that time.
Some of the specific predetermined modes include the engine operating in a deceleration fuel cutoff mode, an active cleaning mode, a service mode, or an engine-off mode. Obviously other opportune modes may occur to one skilled in the art. The oil control valve cleaning routine comprises cycling the oil control valve over its range of operating positions at least once. This allows a regular flow of oil across the valve over its entire range of operating positions to flush and purge, thus forestalling a build-up of any contaminants during the life of the engine.
A preferred aspect of the invention includes a method for removing contaminants from an oil control valve used in a variable cam phasing system of an internal combustion engine.
Another aspect of the invention contemplates a controller for an oil control valve for use in an internal combustion engine. The controller is operable to execute an oil control valve cleaning routine when it is determined that the engine is operating in a predetermined mode. These and other objects of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the embodiments.